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Anion Levels (anion + level)

Distribution by Scientific Domains

Medical Sciences	60%

Selected Abstracts

Uniform corrosion of titanium in alkaline hydrogen peroxide conditions: influence of transition metals and inhibitors calcium and silicate

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2002
J. Rämö
Uniform corrosion of titanium was studied in alkaline hydrogen peroxide environments simulating pulp bleaching conditions. Corrosion rates of unalloyed Grade 2 and alloyed Grade 5 were determined as a function of hydrogen peroxide anion (HOO,) concentration. Influences of calcium and silicate inhibitors and iron and manganese were investigated. Without inhibition titanium corroded at HOO, content of 200 mg/l: Grade 2 0.4 mm/y and Grade 5 1.4 mm/y. Addition of calcium (Ca2+) and silicate (SiO32,) diminished the corrosion of Grade 2 to critical anion level 400 mg/l, but could not protect Grade 5 even at the HOO, concentration of 300 mg/l. Presence of iron and manganese raised the critical levels of the both grades. High HOO, anion level was observed as a notable potential difference between titanium and platinum. Gleichmäßige Flächenkorrosion von Titan unter alkalischen Wasserstoffperoxidbedingungen: Einfluss der Übergangsmetalle und der Inhibitoren Kalzium und Silikat Gleichmäßige Flächenkorrosion von Titan wurde in alkalischen Wasserstoffperoxidbedingungen, die Papierbleichbedingungen simulieren, untersucht. Die Korrosionsgeschwindigkeiten von unlegierter Güteklasse 2 und legierter Güteklasse 5 wurden als Funktion der Wasserstoffperoxidanionen(HOO,)konzentration bestimmt. Einflüsse von Kalzium- und Silikatinhibitoren sowie von Eisen und Mangan wurden untersucht. Ohne Inhibierung betrug die Korrosion von Titan bei einem HOO, -Gehalt von 200 mg/l bei der Güteklasse 2 0,4 mm/Jahr und bei der Güteklasse 5 1,4 mm Jahr. Die Zugabe von Kalzium (Ca2+) und Silikat (SiO32,) verminderte die Korrosion der Güteklasse 2 auf ein kritisches Anionenniveau von 400 mg/l; konnte aber Güteklasse 5 selbst bei einer HOO, -Konzentration von 300 mg/l nicht schützen. Die Anwesenheit von Eisen und Mangan erhöhte die kritischen Niveaus für beide Güteklassen. Hohe HOO, -Anionengehalte wurden als beträchtliche Potentialdifferenz zwischen Titan und Platin beobachtet. [source]

Histamine-3 receptor antagonists reduce superoxide anion generation and lipid peroxidation in rat brain homogenates

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2005
H. E. Badenhorst
Using a cyanide model to induce neurotoxic effects in rat brain homogenates, we examined the neuroprotective properties of three H3 antagonists, namely clobenpropit, thioperamide and impentamine, and compared them to aspirin, a known neuroprotective agent. Superoxide anion levels and malondialdehyde concentration were assessed using the nitroblue tetrazolium and lipid peroxidation assays. Clobenpropit and thioperamide significantly reduced superoxide anion generation and lipid peroxidation. Impentamine reduced lipid peroxidation at all concentrations used, but only reduced superoxide anion generation at a concentration of 1 mM. In the lipid peroxidation assay, all the drugs compared favourably to aspirin. This study demonstrates the potential of these agents to be neuroprotective by exerting antioxidant effects. [source]

Melatonin Counteracts Alterations in Oxidative Metabolism and Cell Viability Induced by Intracellular Calcium Overload in Human Leucocytes: Changes with Age

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2010
Javier Espino
In fact, the free radical theory of ageing proposes that deleterious actions of free radicals are responsible for the functional deterioration associated with ageing. Moreover, a close relationship exists between calcium homeostasis and oxidative stress. The current work was aimed at proving that intracellular calcium overload induced by N -formyl-methionyl-leucyl-phenylalanine (FMLP) and/or thapsigargin leads to oxidative stress. We additionally examined the effect of melatonin on the levels of reactive oxygen species (ROS) and cell viability in human leucocytes collected from young (20,30-year-old) and elderly (65,75-year-old) individuals under both basal and oxidative stress-induced conditions. Treatments with 10 nM FMLP and/or 1 ,M thapsigargin induced a transient increase in cytosolic free-calcium concentration ([Ca2 + ]c) in human leucocytes due to calcium release from internal stores, and led in turn to oxidative stress, as assessed by intracellular ROS measurement. Non-treated leucocytes from aged individuals exhibited higher ROS levels and lower rates of cell survival when compared to leucocytes from young individuals. Similar results were obtained in FMLP and/or thapsigargin-treated leucocytes from elderly individuals when compared to those from the young individuals. Melatonin treatment significantly reduced both hydrogen peroxide (H2O2) and superoxide anion levels, likely due to its free-radical scavenging properties, and enhanced leucocyte viability in both age groups. Therefore, melatonin may be a useful tool for the treatment of disease states and processes where an excessive production of oxidative damage occurs. [source]

Mechanisms involved in the early increase of serotonin contraction evoked by endotoxin in rat middle cerebral arteries

BRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2003
Raquel Hernanz
The present study investigated the mechanisms involved in the increased 5-hydroxytryptamine (5-HT) vasoconstriction observed in rat middle cerebral arteries exposed in vitro to lipopolysaccharide (LPS, 10 ,g ml,1) for 1,5 h. Functional, immunohistochemical and Western blot analysis and superoxide anion measurements by ethidium fluorescence were performed. LPS exposure increased 5-HT (10 ,M) vasoconstriction only during the first 4 h. In contrast to control tissue, indomethacin (10 ,M), the COX-2 inhibitor NS 398 (10 ,M), the TXA2/PGH2 receptor antagonist SQ 29,548 (1 ,M) and the TXA2 synthase inhibitor furegrelate (1 ,M) reduced 5-HT contraction of LPS-treated arteries from hour one. The iNOS inhibitor aminoguanidine (0.1 mM) increased 5-HT contraction from hour three of LPS incubation. The superoxide anion scavenger superoxide dismutase (SOD, 100 U ml,1) and the H2O2 scavenger catalase (1000 U ml,1), as well as the respective inhibitors of NAD(P)H oxidase and xanthine oxidase, apocynin (0.3 mM) and allopurinol (0.3 mM), reduced 5-HT contraction after LPS incubation. LPS induced an increase in superoxide anion levels that was abolished by PEG-SOD. Subthreshold concentrations of the TXA2 analogue U 46619, xanthine/xanthine oxidase and H2O2 potentiated, whereas those of sodium nitroprusside inhibited, the 5-HT contraction. COX-2 expression was increased at 1 and 5 h of LPS incubation, while that of iNOS, Cu/Zn-SOD and Mn-SOD was only increased after 5 h. All the three vascular layers expressed COX-2 and Cu/Zn-SOD. iNOS expression was detected in the endothelium and adventitia after LPS. In conclusion, increased production of TXA2 from COX-2, superoxide anion and H2O2 enhanced vasoconstriction to 5-HT during the first few hours of LPS exposure; iNOS and SOD expression counteracted that increase at 5 h. These changes can contribute to the disturbance of cerebral blood flow in endotoxic shock. British Journal of Pharmacology (2003) 140, 671,680. doi:10.1038/sj.bjp.0705501 [source]